During the treatment of metal or steel melts in treatment refractorily lined vessels such as, for example transport or, casting ladles, violent reactions between the metal and the slag or blown-in inert or reaction gases can occur or can be caused which can cause a major ejection of metal and slag across the rim of the treatment vessel. During a treatment of the metal or the slag in open air as well as in a closed treatment vessel which can be under vacuum, such ejection occurrences are undesired because, apart from the massive contamination of the environment of the treatment vessel and the treatment vessel itself, an uncontrollable loss of metal and slag is involved.
For these reasons, for such treatment steps of metal or slag, covers for covering the treatment vessel are used which often are simple, uncooled and consist at least partially of ceramic materials in the form of a coating and the behavior of which, however, is dissatisfying because the ceramic materials of the cover react with the slag or the metal and thereby, on the one hand, their durability is reduced and, on the other, they chip off to some extent so that by such ceramic parts, the composition of the slag and the metal can be negatively influenced.
On the other hand, also known are water-cooled cover constructions which in most cases consist of steel tubes or boiler tubes which are arranged on top of each other and are welded together and which, due to their structure, have a number of grooves. In these grooves, metal and slag splashes can get caught and form a basis for the possibility that further splashes can accumulate and stick thereon so that in the extreme case, despite water-cooling the tubes, a dome of sticking and partially welded metal and slag splashes is built up which, during a longer lasting treatment of a steel melt with a weight of, for example, 50 t-80 t, can easily reach a weight of several tons. Depending on the formation of said dome it can happen that the cover can be removed only with difficulties or that parts of the dome break again and fall into the melt and again cause undesired reactions and a disturbance of the temperature balance therein.
It can also happen that the dome of metal and slag splashes sticking on the cover is lifted off together with the latter and falls off in an uncontrolled manner during the transport or at a later time which, besides other inconveniences, represents a significant hazard.
However, in this case, residues of metal and slag splashes adhering on the cover have to be removed prior to the next use because if such residues fall down at a next melt, the same can be contaminated in an unacceptable manner.
In some cases it has happened that the dome consisting of metal and slag splashes remained on the treatment vessel after removing the cover and thereby has interfered with the further treatment of the melt because said treatment could only be continued after the removal of the dome. Even if there are no other problems, this, depending on the duration of the work, has a negative effect on the temperature course within the treatment vessel and thus is undesired or even unacceptable if no possibility for reheating the treatment vessel or the mass to be treated is available.